Passage technology was introduced by Sony in 2002 and is relatively new in the communications field. The technology allows equipment from multiple vendors to co-exist on legacy digital cable television (CATV) networks. Passage technology supports multiple conditional access (CA) systems, and it treats each CA system independently. Passage also allows each CA system to operate on its own encrypted data. During encoding, only certain data may be selected for encryption. This process allows multiple conditional access systems to co-exist in an existing cable plant. An additional benefit is that passage technology supports digital video broadcast (DVB) open standards. The DVB open standards have been extended to allow communication to a passage encoding device, for example. Support for DVB open standards allows interchangeable headend equipment operation, and interoperability of multiple CA systems.
During encoding of a passage stream, vital data, essential for decoding, may be selected, duplicated, and encrypted once for legacy set-top boxes (STBs) and once for Passage STBs. Each STB may receive the same transport data and may appropriately select its STB-specific encrypted data. General, non-STB specific content may be shared by all STBs. In this regard, only the critical data necessary for recovering video or audio content may need to be encrypted, and the passage system may only encrypt critical data. If a decoder cannot receive the critical data, then the video image cannot be decompressed.
During decoding of a passage stream, a conventional set-top box (STB) receiver, for example, may utilize a plurality of on-chip memories to store received encoded data as well as decoded passage stream data prior to displaying. Utilizing separate memories for recording encoded passage stream information and decoded information significantly reduces the processing efficiency of the STB and increases implementation cost.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.